There exist various acoustic devices for reducing ambient noise, notably headphones including an active noise reduction system. Generally, such headphones include two microphones, conventionally positioned on the ears of a user. Each earphone is equipped with a microphone capable of sensing a sound signal representative of ambient noise, said noise signal. Active noise reduction is then produced by emitting through the earphones, at the inlet of the ear canal of the user, an airborne sound signal which is calculated in order to compensate for the sensed noise signal, also called counter-noise .